Chrome: Chrome's interface is already minimalist and compact but if you want to shrink it even further you can collapse the page menu into the wrench menu with a simple command-line flag.

You'll need to be rocking a current version of the Google Chrome Development Channel build—stable release users will likely get the collapsed-menu feature soon. If you're the kind of person that likes to tinker with their browser via command-flags you're likely already sporting the development channel build anyway.

All you need to do to enable the collapsed-menu is add --new-wrench-menu as a command-line flag in the shortcut you use to launch Google Chrome. On next launch all your Chrome menus will be collapsed into the single wrench icon. Have a Chrome hack to share? Let's hear about it in the comments.